First commit to migrate the following articles from core-java:

* to core-java-lang:
  * https://www.baeldung.com/java-reflection
  * https://www.baeldung.com/java-generics
  * https://www.baeldung.com/java-eclipse-equals-and-hashcode
  * https://www.baeldung.com/java-chained-exceptions
  * https://www.baeldung.com/java-primitive-conversions //to package
  * https://www.baeldung.com/java-method-reflection
  * https://www.baeldung.com/java-enum-iteration
  * https://www.baeldung.com/java-reflection-change-annotation-params
  * https://www.baeldung.com/java-dynamic-proxies
  * https://www.baeldung.com/java-double-brace-initialization
  * https://www.baeldung.com/java-hashcode
  * https://www.baeldung.com/java-diamond-operator
  * https://www.baeldung.com/java-static (?https://github.com/eugenp/tutorials/pull/3392)
  * https://www.baeldung.com/java-comparator-comparable
  * https://www.baeldung.com/java-continue-and-break
  * https://www.baeldung.com/java-initialization
  * https://www.baeldung.com/java-nested-classes
  * https://www.baeldung.com/java-loops
  * https://www.baeldung.com/java-varargs

core-java-lang/src/main/java/com/baeldung/breakcontinue/BreakContinue.java

@@ -0,0 +1,139 @@
+package com.baeldung.breakcontinue;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+
+/**
+ * @author Santosh
+ *
+ */
+
+public class BreakContinue {
+
+    public static int unlabeledBreak() {
+        String searchName = "Wilson";
+        int counter = 0;
+        List<String> names = Arrays.asList("John", "Peter", "Robert", "Wilson", "Anthony", "Donald", "Richard");
+
+        for (String name : names) {
+            counter++;
+            if (name.equalsIgnoreCase(searchName)) {
+                break;
+            }
+        }
+
+        return counter;
+    }
+
+    public static int unlabeledBreakNestedLoops() {
+        String searchName = "Wilson";
+        int counter = 0;
+        Map<String, List<String>> nameMap = new HashMap<>();
+        nameMap.put("Grade1", Arrays.asList("John", "Peter", "Robert", "Wilson"));
+        nameMap.put("Grade2", Arrays.asList("Anthony", "Donald", "Richard", "Arnold"));
+        nameMap.put("Grade3", Arrays.asList("Wilson", "Michael", "Stephen", "Ryan"));
+
+        Iterator<Entry<String, List<String>>> iterator = nameMap.entrySet()
+            .iterator();
+        Entry<String, List<String>> entry = null;
+        List<String> names = null;
+        while (iterator.hasNext()) {
+            entry = iterator.next();
+            names = entry.getValue();
+            for (String name : names) {
+                if (name.equalsIgnoreCase(searchName)) {
+                    counter++;
+                    break;
+                }
+            }
+        }
+
+        return counter;
+    }
+
+    public static int labeledBreak() {
+        String searchName = "Wilson";
+        int counter = 0;
+        Map<String, List<String>> nameMap = new HashMap<>();
+        nameMap.put("Grade1", Arrays.asList("John", "Peter", "Robert", "Wilson"));
+        nameMap.put("Grade2", Arrays.asList("Anthony", "Donald", "Richard", "Arnold"));
+        nameMap.put("Grade3", Arrays.asList("Wilson", "Michael", "Stephen", "Ryan"));
+
+        Iterator<Entry<String, List<String>>> iterator = nameMap.entrySet()
+            .iterator();
+        Entry<String, List<String>> entry = null;
+        List<String> names = null;
+        compare: 
+        while (iterator.hasNext()) {
+            entry = iterator.next();
+            names = entry.getValue();
+            for (String name : names) {
+                if (name.equalsIgnoreCase(searchName)) {
+                    counter++;
+                    break compare;
+                }
+            }
+        }
+
+        return counter;
+    }
+
+    public static int unlabeledContinue() {
+        String searchName = "Wilson";
+        int counter = 0;
+        Map<String, List<String>> nameMap = new HashMap<>();
+        nameMap.put("Grade1", Arrays.asList("John", "Wilson", "Robert", "Wilson"));
+        nameMap.put("Grade2", Arrays.asList("Anthony", "Donald", "Wilson", "Arnold"));
+        nameMap.put("Grade3", Arrays.asList("Wilson", "Michael", "Wilson", "Ryan"));
+
+        Iterator<Entry<String, List<String>>> iterator = nameMap.entrySet()
+            .iterator();
+        Entry<String, List<String>> entry = null;
+        List<String> names = null;
+        while (iterator.hasNext()) {
+            entry = iterator.next();
+            names = entry.getValue();
+            for (String name : names) {
+                if (!name.equalsIgnoreCase(searchName)) {
+                    continue;
+                }
+
+                counter++;
+            }
+        }
+
+        return counter;
+    }
+
+    public static int labeledContinue() {
+        String searchName = "Wilson";
+        int counter = 0;
+        Map<String, List<String>> nameMap = new HashMap<>();
+        nameMap.put("Grade1", Arrays.asList("John", "Wilson", "Robert", "Wilson"));
+        nameMap.put("Grade2", Arrays.asList("Anthony", "Donald", "Wilson", "Arnold"));
+        nameMap.put("Grade3", Arrays.asList("Wilson", "Michael", "Wilson", "Ryan"));
+
+        Iterator<Entry<String, List<String>>> iterator = nameMap.entrySet()
+            .iterator();
+        Entry<String, List<String>> entry = null;
+        List<String> names = null;
+        compare: 
+        while (iterator.hasNext()) {
+            entry = iterator.next();
+            names = entry.getValue();
+            for (String name : names) {
+                if (name.equalsIgnoreCase(searchName)) {
+                    counter++;
+                    continue compare;
+                }
+            }
+        }
+
+        return counter;
+    }
+
+}

core-java-lang/src/main/java/com/baeldung/chainedexception/LogWithChain.java

@@ -0,0 +1,41 @@
+package com.baeldung.chainedexception;
+
+import com.baeldung.chainedexception.exceptions.GirlFriendOfManagerUpsetException;
+import com.baeldung.chainedexception.exceptions.ManagerUpsetException;
+import com.baeldung.chainedexception.exceptions.NoLeaveGrantedException;
+import com.baeldung.chainedexception.exceptions.TeamLeadUpsetException;
+
+public class LogWithChain {
+
+    public static void main(String[] args) throws Exception {
+        getLeave();
+    }
+
+    private static void getLeave() throws NoLeaveGrantedException {
+        try {
+            howIsTeamLead();
+        } catch (TeamLeadUpsetException e) {
+            throw new NoLeaveGrantedException("Leave not sanctioned.", e);
+        }
+    }
+
+    private static void howIsTeamLead() throws TeamLeadUpsetException {
+        try {
+            howIsManager();
+        } catch (ManagerUpsetException e) {
+            throw new TeamLeadUpsetException("Team lead is not in good mood", e);
+        }
+    }
+
+    private static void howIsManager() throws ManagerUpsetException {
+        try {
+            howIsGirlFriendOfManager();
+        } catch (GirlFriendOfManagerUpsetException e) {
+            throw new ManagerUpsetException("Manager is in bad mood", e);
+        }
+    }
+
+    private static void howIsGirlFriendOfManager() throws GirlFriendOfManagerUpsetException {
+        throw new GirlFriendOfManagerUpsetException("Girl friend of manager is in bad mood");
+    }
+}

core-java-lang/src/main/java/com/baeldung/chainedexception/LogWithoutChain.java

@@ -0,0 +1,44 @@
+package com.baeldung.chainedexception;
+
+import com.baeldung.chainedexception.exceptions.GirlFriendOfManagerUpsetException;
+import com.baeldung.chainedexception.exceptions.ManagerUpsetException;
+import com.baeldung.chainedexception.exceptions.NoLeaveGrantedException;
+import com.baeldung.chainedexception.exceptions.TeamLeadUpsetException;
+
+public class LogWithoutChain {
+
+    public static void main(String[] args) throws Exception {
+        getLeave();
+    }
+
+    private static void getLeave() throws NoLeaveGrantedException {
+        try {
+            howIsTeamLead();
+        } catch (TeamLeadUpsetException e) {
+            e.printStackTrace();
+            throw new NoLeaveGrantedException("Leave not sanctioned.");
+        }
+    }
+
+    private static void howIsTeamLead() throws TeamLeadUpsetException {
+        try {
+            howIsManager();
+        } catch (ManagerUpsetException e) {
+            e.printStackTrace();
+            throw new TeamLeadUpsetException("Team lead is not in good mood");
+        }
+    }
+
+    private static void howIsManager() throws ManagerUpsetException {
+        try {
+            howIsGirlFriendOfManager();
+        } catch (GirlFriendOfManagerUpsetException e) {
+            e.printStackTrace();
+            throw new ManagerUpsetException("Manager is in bad mood");
+        }
+    }
+
+    private static void howIsGirlFriendOfManager() throws GirlFriendOfManagerUpsetException {
+        throw new GirlFriendOfManagerUpsetException("Girl friend of manager is in bad mood");
+    }
+}

core-java-lang/src/main/java/com/baeldung/chainedexception/exceptions/GirlFriendOfManagerUpsetException.java

@@ -0,0 +1,12 @@
+package com.baeldung.chainedexception.exceptions;
+
+public class GirlFriendOfManagerUpsetException extends Exception {
+
+    public GirlFriendOfManagerUpsetException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public GirlFriendOfManagerUpsetException(String message) {
+        super(message);
+    }
+}

core-java-lang/src/main/java/com/baeldung/chainedexception/exceptions/ManagerUpsetException.java

@@ -0,0 +1,12 @@
+package com.baeldung.chainedexception.exceptions;
+
+public class ManagerUpsetException extends Exception {
+
+    public ManagerUpsetException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public ManagerUpsetException(String message) {
+        super(message);
+    }
+}

core-java-lang/src/main/java/com/baeldung/chainedexception/exceptions/NoLeaveGrantedException.java

@@ -0,0 +1,12 @@
+package com.baeldung.chainedexception.exceptions;
+
+public class NoLeaveGrantedException extends Exception {
+
+    public NoLeaveGrantedException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public NoLeaveGrantedException(String message) {
+        super(message);
+    }
+}

core-java-lang/src/main/java/com/baeldung/chainedexception/exceptions/TeamLeadUpsetException.java

@@ -0,0 +1,12 @@
+package com.baeldung.chainedexception.exceptions;
+
+public class TeamLeadUpsetException extends Exception {
+
+    public TeamLeadUpsetException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public TeamLeadUpsetException(String message) {
+        super(message);
+    }
+}

core-java-lang/src/main/java/com/baeldung/comparable/Player.java

@@ -0,0 +1,51 @@
+package com.baeldung.comparable;
+
+public class Player implements Comparable<Player> {
+
+    private int ranking;
+
+    private String name;
+
+    private int age;
+
+    public Player(int ranking, String name, int age) {
+        this.ranking = ranking;
+        this.name = name;
+        this.age = age;
+    }
+
+    public int getRanking() {
+        return ranking;
+    }
+
+    public void setRanking(int ranking) {
+        this.ranking = ranking;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    public void setAge(int age) {
+        this.age = age;
+    }
+
+    @Override
+    public String toString() {
+        return this.name;
+    }
+
+    @Override
+    public int compareTo(Player otherPlayer) {
+        return (this.getRanking() - otherPlayer.getRanking());
+    }
+
+}

core-java-lang/src/main/java/com/baeldung/comparable/PlayerSorter.java

@@ -0,0 +1,25 @@
+package com.baeldung.comparable;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+public class PlayerSorter {
+
+    public static void main(String[] args) {
+
+        List<Player> footballTeam = new ArrayList<Player>();
+        Player player1 = new Player(59, "John", 20);
+        Player player2 = new Player(67, "Roger", 22);
+        Player player3 = new Player(45, "Steven", 24);
+        footballTeam.add(player1);
+        footballTeam.add(player2);
+        footballTeam.add(player3);
+
+        System.out.println("Before Sorting : " + footballTeam);
+        Collections.sort(footballTeam);
+        System.out.println("After Sorting : " + footballTeam);
+
+    }
+
+}

core-java-lang/src/main/java/com/baeldung/comparator/Player.java

@@ -0,0 +1,46 @@
+package com.baeldung.comparator;
+
+public class Player {
+
+    private int ranking;
+
+    private String name;
+
+    private int age;
+
+    public Player(int ranking, String name, int age) {
+        this.ranking = ranking;
+        this.name = name;
+        this.age = age;
+    }
+
+    public int getRanking() {
+        return ranking;
+    }
+
+    public void setRanking(int ranking) {
+        this.ranking = ranking;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    public void setAge(int age) {
+        this.age = age;
+    }
+
+    @Override
+    public String toString() {
+        return this.name;
+    }
+
+}

core-java-lang/src/main/java/com/baeldung/comparator/PlayerAgeComparator.java

@@ -0,0 +1,12 @@
+package com.baeldung.comparator;
+
+import java.util.Comparator;
+
+public class PlayerAgeComparator implements Comparator<Player> {
+
+    @Override
+    public int compare(Player firstPlayer, Player secondPlayer) {
+       return (firstPlayer.getAge() - secondPlayer.getAge());
+    }
+
+}

core-java-lang/src/main/java/com/baeldung/comparator/PlayerAgeSorter.java

@@ -0,0 +1,27 @@
+package com.baeldung.comparator;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+public class PlayerAgeSorter {
+
+    public static void main(String[] args) {
+        
+        List<Player> footballTeam = new ArrayList<Player>();
+        Player player1 = new Player(59, "John", 22);
+        Player player2 = new Player(67, "Roger", 20);
+        Player player3 = new Player(45, "Steven", 24);
+        footballTeam.add(player1);
+        footballTeam.add(player2);
+        footballTeam.add(player3);
+        
+        System.out.println("Before Sorting : " + footballTeam);
+        //Instance of PlayerAgeComparator
+        PlayerAgeComparator playerComparator = new PlayerAgeComparator();
+        Collections.sort(footballTeam, playerComparator);
+        System.out.println("After Sorting by age : " + footballTeam);
+        
+    }
+
+}

core-java-lang/src/main/java/com/baeldung/comparator/PlayerRankingComparator.java

@@ -0,0 +1,12 @@
+package com.baeldung.comparator;
+
+import java.util.Comparator;
+
+public class PlayerRankingComparator implements Comparator<Player> {
+
+    @Override
+    public int compare(Player firstPlayer, Player secondPlayer) {
+       return (firstPlayer.getRanking() - secondPlayer.getRanking());
+    }
+
+}

core-java-lang/src/main/java/com/baeldung/comparator/PlayerRankingSorter.java

@@ -0,0 +1,27 @@
+package com.baeldung.comparator;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+public class PlayerRankingSorter {
+
+    public static void main(String[] args) {
+        
+        List<Player> footballTeam = new ArrayList<Player>();
+        Player player1 = new Player(59, "John", 22);
+        Player player2 = new Player(67, "Roger", 20);
+        Player player3 = new Player(45, "Steven", 40);
+        footballTeam.add(player1);
+        footballTeam.add(player2);
+        footballTeam.add(player3);
+        
+        System.out.println("Before Sorting : " + footballTeam);
+        //Instance of PlayerRankingComparator
+        PlayerRankingComparator playerComparator = new PlayerRankingComparator();
+        Collections.sort(footballTeam, playerComparator);
+        System.out.println("After Sorting by ranking : " + footballTeam);
+        
+    }
+
+}

core-java-lang/src/main/java/com/baeldung/dynamicproxy/DynamicInvocationHandler.java

@@ -0,0 +1,19 @@
+package com.baeldung.dynamicproxy;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.Method;
+
+public class DynamicInvocationHandler implements InvocationHandler {
+
+    private static Logger LOGGER = LoggerFactory.getLogger(DynamicInvocationHandler.class);
+
+    @Override
+    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
+        LOGGER.info("Invoked method: {}", method.getName());
+
+        return 42;
+    }
+}

core-java-lang/src/main/java/com/baeldung/dynamicproxy/TimingDynamicInvocationHandler.java

@@ -0,0 +1,36 @@
+package com.baeldung.dynamicproxy;
+
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.Method;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class TimingDynamicInvocationHandler implements InvocationHandler {
+
+    private static Logger LOGGER = LoggerFactory.getLogger(TimingDynamicInvocationHandler.class);
+    private final Map<String, Method> methods = new HashMap<>();
+
+    private Object target;
+
+    TimingDynamicInvocationHandler(Object target) {
+        this.target = target;
+
+        for(Method method: target.getClass().getDeclaredMethods()) {
+            this.methods.put(method.getName(), method);
+        }
+    }
+
+    @Override
+    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
+        long start = System.nanoTime();
+        Object result = methods.get(method.getName()).invoke(target, args);
+        long elapsed = System.nanoTime() - start;
+
+        LOGGER.info("Executing {} finished in {} ns", method.getName(), elapsed);
+
+        return result;
+    }
+}

core-java-lang/src/main/java/com/baeldung/equalshashcode/entities/ComplexClass.java

@@ -0,0 +1,63 @@
+package com.baeldung.equalshashcode.entities;
+
+import java.util.List;
+import java.util.Set;
+
+public class ComplexClass {
+
+    private List<?> genericList;
+    private Set<Integer> integerSet;
+
+    public ComplexClass(List<?> genericArrayList, Set<Integer> integerHashSet) {
+        super();
+        this.genericList = genericArrayList;
+        this.integerSet = integerHashSet;
+    }
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + ((genericList == null) ? 0 : genericList.hashCode());
+        result = prime * result + ((integerSet == null) ? 0 : integerSet.hashCode());
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (!(obj instanceof ComplexClass))
+            return false;
+        ComplexClass other = (ComplexClass) obj;
+        if (genericList == null) {
+            if (other.genericList != null)
+                return false;
+        } else if (!genericList.equals(other.genericList))
+            return false;
+        if (integerSet == null) {
+            if (other.integerSet != null)
+                return false;
+        } else if (!integerSet.equals(other.integerSet))
+            return false;
+        return true;
+    }
+
+    protected List<?> getGenericList() {
+        return genericList;
+    }
+
+    protected void setGenericArrayList(List<?> genericList) {
+        this.genericList = genericList;
+    }
+
+    protected Set<Integer> getIntegerSet() {
+        return integerSet;
+    }
+
+    protected void setIntegerSet(Set<Integer> integerSet) {
+        this.integerSet = integerSet;
+    }
+}

core-java-lang/src/main/java/com/baeldung/equalshashcode/entities/PrimitiveClass.java

@@ -0,0 +1,54 @@
+package com.baeldung.equalshashcode.entities;
+
+public class PrimitiveClass {
+
+    private boolean primitiveBoolean;
+    private int primitiveInt;
+
+    public PrimitiveClass(boolean primitiveBoolean, int primitiveInt) {
+        super();
+        this.primitiveBoolean = primitiveBoolean;
+        this.primitiveInt = primitiveInt;
+    }
+
+    protected boolean isPrimitiveBoolean() {
+        return primitiveBoolean;
+    }
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + (primitiveBoolean ? 1231 : 1237);
+        result = prime * result + primitiveInt;
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        PrimitiveClass other = (PrimitiveClass) obj;
+        if (primitiveBoolean != other.primitiveBoolean)
+            return false;
+        if (primitiveInt != other.primitiveInt)
+            return false;
+        return true;
+    }
+
+    protected void setPrimitiveBoolean(boolean primitiveBoolean) {
+        this.primitiveBoolean = primitiveBoolean;
+    }
+
+    protected int getPrimitiveInt() {
+        return primitiveInt;
+    }
+
+    protected void setPrimitiveInt(int primitiveInt) {
+        this.primitiveInt = primitiveInt;
+    }
+}

core-java-lang/src/main/java/com/baeldung/equalshashcode/entities/Rectangle.java

@@ -0,0 +1,58 @@
+package com.baeldung.equalshashcode.entities;
+
+public class Rectangle extends Shape {
+    private double width;
+    private double length;
+
+    public Rectangle(double width, double length) {
+        this.width = width;
+        this.length = length;
+    }
+
+    @Override
+    public double area() {
+        return width * length;
+    }
+
+    @Override
+    public double perimeter() {
+        return 2 * (width + length);
+    }
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        long temp;
+        temp = Double.doubleToLongBits(length);
+        result = prime * result + (int) (temp ^ (temp >>> 32));
+        temp = Double.doubleToLongBits(width);
+        result = prime * result + (int) (temp ^ (temp >>> 32));
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        Rectangle other = (Rectangle) obj;
+        if (Double.doubleToLongBits(length) != Double.doubleToLongBits(other.length))
+            return false;
+        if (Double.doubleToLongBits(width) != Double.doubleToLongBits(other.width))
+            return false;
+        return true;
+    }
+
+    protected double getWidth() {
+        return width;
+    }
+
+    protected double getLength() {
+        return length;
+    }
+
+}

core-java-lang/src/main/java/com/baeldung/equalshashcode/entities/Shape.java

@@ -0,0 +1,7 @@
+package com.baeldung.equalshashcode.entities;
+
+public abstract class Shape {
+    public abstract double area();
+
+    public abstract double perimeter();
+}

core-java-lang/src/main/java/com/baeldung/equalshashcode/entities/Square.java

@@ -0,0 +1,58 @@
+package com.baeldung.equalshashcode.entities;
+
+import java.awt.*;
+
+public class Square extends Rectangle {
+
+    private Color color;
+
+    public Square(double width, Color color) {
+        super(width, width);
+        this.color = color;
+    }
+
+    /* (non-Javadoc)
+     * @see java.lang.Object#hashCode()
+     */
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = super.hashCode();
+        result = prime * result + ((color == null) ? 0 : color.hashCode());
+        return result;
+    }
+
+    /* (non-Javadoc)
+     * @see java.lang.Object#equals(java.lang.Object)
+     */
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (!super.equals(obj)) {
+            return false;
+        }
+        if (!(obj instanceof Square)) {
+            return false;
+        }
+        Square other = (Square) obj;
+        if (color == null) {
+            if (other.color != null) {
+                return false;
+            }
+        } else if (!color.equals(other.color)) {
+            return false;
+        }
+        return true;
+    }
+
+    protected Color getColor() {
+        return color;
+    }
+
+    protected void setColor(Color color) {
+        this.color = color;
+    }
+
+}

core-java-lang/src/main/java/com/baeldung/generics/Building.java

@@ -0,0 +1,12 @@
+package com.baeldung.generics;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class Building {
+    private static final Logger LOGGER = LoggerFactory.getLogger(Building.class);
+
+    public void paint() {
+        LOGGER.info("Painting Building");
+    }
+}

core-java-lang/src/main/java/com/baeldung/generics/Generics.java

@@ -0,0 +1,31 @@
+package com.baeldung.generics;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+public class Generics {
+
+    // definition of a generic method
+    public static <T> List<T> fromArrayToList(T[] a) {
+        return Arrays.stream(a).collect(Collectors.toList());
+    }
+
+    // definition of a generic method
+    public static <T, G> List<G> fromArrayToList(T[] a, Function<T, G> mapperFunction) {
+        return Arrays.stream(a).map(mapperFunction).collect(Collectors.toList());
+    }
+
+    // example of a generic method that has Number as an upper bound for T
+    public static <T extends Number> List<T> fromArrayToListWithUpperBound(T[] a) {
+        return Arrays.stream(a).collect(Collectors.toList());
+    }
+
+    // example of a generic method with a wild card, this method can be used
+    // with a list of any subtype of Building
+    public static void paintAllBuildings(List<? extends Building> buildings) {
+        buildings.forEach(Building::paint);
+    }
+
+}

core-java-lang/src/main/java/com/baeldung/generics/House.java

@@ -0,0 +1,12 @@
+package com.baeldung.generics;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class House extends Building {
+    private static final Logger LOGGER = LoggerFactory.getLogger(House.class);
+
+    public void paint() {
+        LOGGER.info("Painting House");
+    }
+}

core-java-lang/src/main/java/com/baeldung/hashcode/entities/User.java

@@ -0,0 +1,42 @@
+package com.baeldung.hashcode.entities;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class User {
+
+    private final Logger logger = LoggerFactory.getLogger(User.class);
+    private long id;
+    private String name;
+    private String email;
+
+    public User(long id, String name, String email) {
+        this.id = id;
+        this.name = name;
+        this.email = email;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o)
+            return true;
+        if (o == null)
+            return false;
+        if (this.getClass() != o.getClass())
+            return false;
+        User user = (User) o;
+        return id == user.id && (name.equals(user.name) && email.equals(user.email));
+    }
+
+    @Override
+    public int hashCode() {
+        int hash = 7;
+        hash = 31 * hash + (int) id;
+        hash = 31 * hash + (name == null ? 0 : name.hashCode());
+        hash = 31 * hash + (email == null ? 0 : email.hashCode());
+        logger.info("hashCode() method called - Computed hash: " + hash);
+        return hash;
+    }
+    // getters and setters here
+    
+}

core-java-lang/src/main/java/com/baeldung/initializationguide/User.java

@@ -0,0 +1,53 @@
+package com.baeldung.initializationguide;
+
+import java.io.Serializable;
+
+public class User implements Serializable, Cloneable {
+    private static final long serialVersionUID = 1L;
+    static String forum;
+    private String name;
+    private int id;
+
+    {
+        id = 0;
+        System.out.println("Instance Initializer");
+    }
+
+    static {
+    	forum = "Java";
+        System.out.println("Static Initializer");
+    }
+
+    public User(String name, int id) {
+        super();
+        this.name = name;
+        this.id = id;
+    }
+
+    public User() {
+        System.out.println("Constructor");
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    @Override
+    protected Object clone() throws CloneNotSupportedException {
+        return this;
+    }
+
+}
+

core-java-lang/src/main/java/com/baeldung/java/reflection/Animal.java

@@ -0,0 +1,23 @@
+package com.baeldung.java.reflection;
+
+public abstract class Animal implements Eating {
+
+    public static final String CATEGORY = "domestic";
+
+    private String name;
+
+    public Animal(String name) {
+        this.name = name;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    protected abstract String getSound();
+
+}

core-java-lang/src/main/java/com/baeldung/java/reflection/Bird.java

@@ -0,0 +1,36 @@
+package com.baeldung.java.reflection;
+
+public class Bird extends Animal {
+    private boolean walks;
+
+    public Bird() {
+        super("bird");
+    }
+
+    public Bird(String name, boolean walks) {
+        super(name);
+        setWalks(walks);
+    }
+
+    public Bird(String name) {
+        super(name);
+    }
+
+    @Override
+    public String eats() {
+        return "grains";
+    }
+
+    @Override
+    protected String getSound() {
+        return "chaps";
+    }
+
+    public boolean walks() {
+        return walks;
+    }
+
+    public void setWalks(boolean walks) {
+        this.walks = walks;
+    }
+}

core-java-lang/src/main/java/com/baeldung/java/reflection/DynamicGreeter.java

@@ -0,0 +1,23 @@
+package com.baeldung.java.reflection;
+
+import java.lang.annotation.Annotation;
+
+public class DynamicGreeter implements Greeter {
+    
+    private String greet;
+
+    public DynamicGreeter(String greet) {
+        this.greet = greet;
+    }
+
+    @Override
+    public Class<? extends Annotation> annotationType() {
+        return DynamicGreeter.class;
+    }
+
+    @Override
+    public String greet() {
+        return greet;
+    }
+
+}

core-java-lang/src/main/java/com/baeldung/java/reflection/Eating.java

@@ -0,0 +1,5 @@
+package com.baeldung.java.reflection;
+
+public interface Eating {
+    String eats();
+}

core-java-lang/src/main/java/com/baeldung/java/reflection/Goat.java

@@ -0,0 +1,24 @@
+package com.baeldung.java.reflection;
+
+public class Goat extends Animal implements Locomotion {
+
+    public Goat(String name) {
+        super(name);
+    }
+
+    @Override
+    protected String getSound() {
+        return "bleat";
+    }
+
+    @Override
+    public String getLocomotion() {
+        return "walks";
+    }
+
+    @Override
+    public String eats() {
+        return "grass";
+    }
+
+}

core-java-lang/src/main/java/com/baeldung/java/reflection/Greeter.java

@@ -0,0 +1,10 @@
+package com.baeldung.java.reflection;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Greeter {
+
+    public String greet() default "";
+}

core-java-lang/src/main/java/com/baeldung/java/reflection/GreetingAnnotation.java

@@ -0,0 +1,58 @@
+package com.baeldung.java.reflection;
+
+import java.lang.annotation.Annotation;
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+import java.util.Map;
+
+public class GreetingAnnotation {
+   
+    private static final String ANNOTATION_METHOD = "annotationData";
+    private static final String ANNOTATION_FIELDS = "declaredAnnotations";
+    private static final String ANNOTATIONS = "annotations";
+
+    public static void main(String ...args) {
+        Greeter greetings = Greetings.class.getAnnotation(Greeter.class);
+        System.err.println("Hello there, " + greetings.greet() + " !!");
+
+        Greeter targetValue = new DynamicGreeter("Good evening");
+        //alterAnnotationValueJDK8(Greetings.class, Greeter.class, targetValue);
+        alterAnnotationValueJDK7(Greetings.class, Greeter.class, targetValue);
+        
+        greetings = Greetings.class.getAnnotation(Greeter.class);
+        System.err.println("Hello there, " + greetings.greet() + " !!");
+    }
+    
+    @SuppressWarnings("unchecked")
+    public static void alterAnnotationValueJDK8(Class<?> targetClass, Class<? extends Annotation> targetAnnotation, Annotation targetValue) {
+        try {
+            Method method = Class.class.getDeclaredMethod(ANNOTATION_METHOD, null);
+            method.setAccessible(true);
+
+            Object annotationData = method.invoke(targetClass);
+            
+            Field annotations = annotationData.getClass().getDeclaredField(ANNOTATIONS);
+            annotations.setAccessible(true);
+
+            Map<Class<? extends Annotation>, Annotation> map = (Map<Class<? extends Annotation>, Annotation>) annotations.get(annotationData);
+            map.put(targetAnnotation, targetValue);
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+    
+    @SuppressWarnings("unchecked")
+    public static void alterAnnotationValueJDK7(Class<?> targetClass, Class<? extends Annotation> targetAnnotation, Annotation targetValue) {
+        try {            
+            Field annotations = Class.class.getDeclaredField(ANNOTATIONS);
+            annotations.setAccessible(true);
+
+            Map<Class<? extends Annotation>, Annotation> map = (Map<Class<? extends Annotation>, Annotation>) annotations.get(targetClass);
+            System.out.println(map);
+            map.put(targetAnnotation, targetValue);
+            System.out.println(map);
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+}

core-java-lang/src/main/java/com/baeldung/java/reflection/Greetings.java

@@ -0,0 +1,6 @@
+package com.baeldung.java.reflection;
+
+@Greeter(greet="Good morning")
+public class Greetings {
+
+}

core-java-lang/src/main/java/com/baeldung/java/reflection/Locomotion.java

@@ -0,0 +1,5 @@
+package com.baeldung.java.reflection;
+
+public interface Locomotion {
+    String getLocomotion();
+}

core-java-lang/src/main/java/com/baeldung/java/reflection/Operations.java

@@ -0,0 +1,21 @@
+package com.baeldung.java.reflection;
+
+public class Operations {
+
+    public double publicSum(int a, double b) {
+        return a + b;
+    }
+
+    public static double publicStaticMultiply(float a, long b) {
+        return a * b;
+    }
+
+    private boolean privateAnd(boolean a, boolean b) {
+        return a && b;
+    }
+
+    protected int protectedMax(int a, int b) {
+        return a > b ? a : b;
+    }
+
+}

core-java-lang/src/main/java/com/baeldung/java/reflection/Person.java

@@ -0,0 +1,6 @@
+package com.baeldung.java.reflection;
+
+public class Person {
+    private String name;
+    private int age;
+}

core-java-lang/src/main/java/com/baeldung/loops/InfiniteLoops.java

@@ -0,0 +1,23 @@
+package com.baeldung.loops;
+
+public class InfiniteLoops {
+
+    public void infiniteLoopUsingWhile() {
+        while (true) {
+            System.out.println("Infinite loop using while");
+        }
+    }
+
+    public void infiniteLoopUsingFor() {
+        for (;;) {
+            System.out.println("Infinite loop using for");
+        }
+    }
+
+    public void infiniteLoopUsingDoWhile() {
+        do {
+            System.out.println("Infinite loop using do-while");
+        } while (true);
+    }
+
+}

core-java-lang/src/main/java/com/baeldung/loops/LoopsInJava.java

@@ -0,0 +1,43 @@
+package com.baeldung.loops;
+
+public class LoopsInJava {
+
+    public int[] simple_for_loop() {
+        int[] arr = new int[5];
+        for (int i = 0; i < 5; i++) {
+            arr[i] = i;
+            System.out.println("Simple for loop: i - " + i);
+        }
+        return arr;
+    }
+
+    public int[] enhanced_for_each_loop() {
+        int[] intArr = { 0, 1, 2, 3, 4 };
+        int[] arr = new int[5];
+        for (int num : intArr) {
+            arr[num] = num;
+            System.out.println("Enhanced for-each loop: i - " + num);
+        }
+        return arr;
+    }
+
+    public int[] while_loop() {
+        int i = 0;
+        int[] arr = new int[5];
+        while (i < 5) {
+            arr[i] = i;
+            System.out.println("While loop: i - " + i++);
+        }
+        return arr;
+    }
+
+    public int[] do_while_loop() {
+        int i = 0;
+        int[] arr = new int[5];
+        do {
+            arr[i] = i;
+            System.out.println("Do-While loop: i - " + i++);
+        } while (i < 5);
+        return arr;
+    }
+}

core-java-lang/src/main/java/com/baeldung/staticdemo/Car.java

@@ -0,0 +1,48 @@
+package com.baeldung.staticdemo;
+
+/**
+ * This class demonstrates the use of static fields and static methods
+ * the instance variables engine and displacement are distinct for 
+ * each and every object whereas static/class variable numberOfCars
+ * is unique and is shared across all objects of this class.
+ * 
+ * @author baeldung
+ *
+ */
+public class Car {
+    private String name;
+    private String engine;
+    
+    public static int numberOfCars;
+    
+    public Car(String name, String engine) {
+        this.name = name;
+        this.engine = engine;
+        numberOfCars++;
+    }
+
+    //getters and setters
+    public static int getNumberOfCars() {
+        return numberOfCars;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getEngine() {
+        return engine;
+    }
+
+    public void setEngine(String engine) {
+        this.engine = engine;
+    }
+
+    public static void setNumberOfCars(int numberOfCars) {
+        Car.numberOfCars = numberOfCars;
+    }
+}

core-java-lang/src/main/java/com/baeldung/staticdemo/Singleton.java

@@ -0,0 +1,13 @@
+package com.baeldung.staticdemo;
+
+public class Singleton  {    
+    private Singleton() {}
+    
+    private static class SingletonHolder {    
+        public static final Singleton instance = new Singleton();
+    }    
+
+    public static Singleton getInstance() {    
+        return SingletonHolder.instance;    
+    }    
+}

core-java-lang/src/main/java/com/baeldung/staticdemo/StaticBlock.java

@@ -0,0 +1,28 @@
+package com.baeldung.staticdemo;
+
+import java.util.LinkedList;
+import java.util.List;
+
+public class StaticBlock {
+    private static List<String> ranks = new LinkedList<>();
+
+    static {
+        ranks.add("Lieutenant");
+        ranks.add("Captain");
+        ranks.add("Major");
+    }
+    
+    static {
+        ranks.add("Colonel");
+        ranks.add("General");
+    }
+
+    //getters and setters
+    public static List<String> getRanks() {
+        return ranks;
+    }
+
+    public static void setRanks(List<String> ranks) {
+        StaticBlock.ranks = ranks;
+    }
+}

core-java-lang/src/test/java/com/baeldung/breakcontinue/BreakContinueUnitTest.java

@@ -0,0 +1,39 @@
+package com.baeldung.breakcontinue;
+
+import static com.baeldung.breakcontinue.BreakContinue.labeledBreak;
+import static com.baeldung.breakcontinue.BreakContinue.labeledContinue;
+import static com.baeldung.breakcontinue.BreakContinue.unlabeledBreak;
+import static com.baeldung.breakcontinue.BreakContinue.unlabeledBreakNestedLoops;
+import static com.baeldung.breakcontinue.BreakContinue.unlabeledContinue;
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class BreakContinueUnitTest {
+
+    @Test
+    public void whenUnlabeledBreak_ThenEqual() {
+        assertEquals(4, unlabeledBreak());
+    }
+
+    @Test
+    public void whenUnlabeledBreakNestedLoops_ThenEqual() {
+        assertEquals(2, unlabeledBreakNestedLoops());
+    }
+
+    @Test
+    public void whenLabeledBreak_ThenEqual() {
+        assertEquals(1, labeledBreak());
+    }
+
+    @Test
+    public void whenUnlabeledContinue_ThenEqual() {
+        assertEquals(5, unlabeledContinue());
+    }
+
+    @Test
+    public void whenLabeledContinue_ThenEqual() {
+        assertEquals(3, labeledContinue());
+    }
+
+}

core-java-lang/src/test/java/com/baeldung/comparable/ComparableUnitTest.java

@@ -0,0 +1,29 @@
+package com.baeldung.comparable;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.junit.Test;
+
+public class ComparableUnitTest {
+
+    @Test
+    public void whenUsingComparable_thenSortedList() {
+        List<Player> footballTeam = new ArrayList<Player>();
+        Player player1 = new Player(59, "John", 20);
+        Player player2 = new Player(67, "Roger", 22);
+        Player player3 = new Player(45, "Steven", 24);
+        footballTeam.add(player1);
+        footballTeam.add(player2);
+        footballTeam.add(player3);
+        Collections.sort(footballTeam);
+        assertEquals(footballTeam.get(0)
+            .getName(), "Steven");
+        assertEquals(footballTeam.get(2)
+            .getRanking(), 67);
+    }
+
+}

core-java-lang/src/test/java/com/baeldung/comparator/ComparatorUnitTest.java

@@ -0,0 +1,47 @@
+package com.baeldung.comparator;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.junit.Before;
+import org.junit.Test;
+
+public class ComparatorUnitTest {
+
+    List<Player> footballTeam;
+
+    @Before
+    public void setUp() {
+        footballTeam = new ArrayList<Player>();
+        Player player1 = new Player(59, "John", 20);
+        Player player2 = new Player(67, "Roger", 22);
+        Player player3 = new Player(45, "Steven", 24);
+        footballTeam.add(player1);
+        footballTeam.add(player2);
+        footballTeam.add(player3);
+    }
+
+    @Test
+    public void whenUsingRankingComparator_thenSortedList() {
+        PlayerRankingComparator playerComparator = new PlayerRankingComparator();
+        Collections.sort(footballTeam, playerComparator);
+        assertEquals(footballTeam.get(0)
+            .getName(), "Steven");
+        assertEquals(footballTeam.get(2)
+            .getRanking(), 67);
+    }
+
+    @Test
+    public void whenUsingAgeComparator_thenSortedList() {
+        PlayerAgeComparator playerComparator = new PlayerAgeComparator();
+        Collections.sort(footballTeam, playerComparator);
+        assertEquals(footballTeam.get(0)
+            .getName(), "John");
+        assertEquals(footballTeam.get(2)
+            .getRanking(), 45);
+    }
+
+}

core-java-lang/src/test/java/com/baeldung/comparator/Java8ComparatorUnitTest.java

@@ -0,0 +1,68 @@
+package com.baeldung.comparator;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+
+import org.junit.Before;
+import org.junit.Test;
+
+public class Java8ComparatorUnitTest {
+
+    List<Player> footballTeam;
+
+    @Before
+    public void setUp() {
+        footballTeam = new ArrayList<Player>();
+        Player player1 = new Player(59, "John", 22);
+        Player player2 = new Player(67, "Roger", 20);
+        Player player3 = new Player(45, "Steven", 24);
+        footballTeam.add(player1);
+        footballTeam.add(player2);
+        footballTeam.add(player3);
+    }
+
+    @Test
+    public void whenComparing_UsingLambda_thenSorted() {
+        System.out.println("************** Java 8 Comaparator **************");
+        Comparator<Player> byRanking = (Player player1, Player player2) -> player1.getRanking() - player2.getRanking();
+
+        System.out.println("Before Sorting : " + footballTeam);
+        Collections.sort(footballTeam, byRanking);
+        System.out.println("After Sorting : " + footballTeam);
+        assertEquals(footballTeam.get(0)
+            .getName(), "Steven");
+        assertEquals(footballTeam.get(2)
+            .getRanking(), 67);
+    }
+
+    @Test
+    public void whenComparing_UsingComparatorComparing_thenSorted() {
+        System.out.println("********* Comaparator.comparing method *********");
+        System.out.println("********* byRanking *********");
+        Comparator<Player> byRanking = Comparator.comparing(Player::getRanking);
+
+        System.out.println("Before Sorting : " + footballTeam);
+        Collections.sort(footballTeam, byRanking);
+        System.out.println("After Sorting : " + footballTeam);
+        assertEquals(footballTeam.get(0)
+            .getName(), "Steven");
+        assertEquals(footballTeam.get(2)
+            .getRanking(), 67);
+        
+        System.out.println("********* byAge *********");
+        Comparator<Player> byAge = Comparator.comparing(Player::getAge);
+
+        System.out.println("Before Sorting : " + footballTeam);
+        Collections.sort(footballTeam, byAge);
+        System.out.println("After Sorting : " + footballTeam);
+        assertEquals(footballTeam.get(0)
+            .getName(), "Roger");
+        assertEquals(footballTeam.get(2)
+            .getRanking(), 45);
+    }
+
+}

core-java-lang/src/test/java/com/baeldung/dynamicproxy/DynamicProxyIntegrationTest.java

@@ -0,0 +1,57 @@
+package com.baeldung.dynamicproxy;
+
+import org.junit.Test;
+
+import java.lang.reflect.Proxy;
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
+
+public class DynamicProxyIntegrationTest {
+
+    @Test
+    public void givenDynamicProxy_thenPutWorks() {
+        Map proxyInstance = (Map) Proxy.newProxyInstance(DynamicProxyIntegrationTest.class.getClassLoader(), new Class[] { Map.class }, new DynamicInvocationHandler());
+
+        proxyInstance.put("hello", "world");
+    }
+
+    @Test
+    public void givenInlineDynamicProxy_thenGetWorksOtherMethodsDoNot() {
+        Map proxyInstance = (Map) Proxy.newProxyInstance(DynamicProxyIntegrationTest.class.getClassLoader(), new Class[] { Map.class }, (proxy, method, methodArgs) -> {
+
+            if (method.getName().equals("get")) {
+                return 42;
+            } else {
+                throw new UnsupportedOperationException("Unsupported method: " + method.getName());
+            }
+        });
+
+        int result = (int) proxyInstance.get("hello");
+
+        assertEquals(42, result);
+
+        try {
+            proxyInstance.put("hello", "world");
+            fail();
+        } catch(UnsupportedOperationException e) {
+            // expected
+        }
+    }
+
+    @Test
+    public void givenTimingDynamicProxy_thenMethodInvokationsProduceTiming() {
+        Map mapProxyInstance = (Map) Proxy.newProxyInstance(DynamicProxyIntegrationTest.class.getClassLoader(), new Class[] { Map.class }, new TimingDynamicInvocationHandler(new HashMap<>()));
+
+        mapProxyInstance.put("hello", "world");
+        assertEquals("world", mapProxyInstance.get("hello"));
+
+        CharSequence csProxyInstance = (CharSequence) Proxy.newProxyInstance(DynamicProxyIntegrationTest.class.getClassLoader(), new Class[] { CharSequence.class }, new TimingDynamicInvocationHandler("Hello World"));
+
+        assertEquals('l', csProxyInstance.charAt(2));
+        assertEquals(11, csProxyInstance.length());
+    }
+
+}

core-java-lang/src/test/java/com/baeldung/equalshashcode/entities/ComplexClassUnitTest.java

@@ -0,0 +1,35 @@
+package com.baeldung.equalshashcode.entities;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import com.baeldung.equalshashcode.entities.ComplexClass;
+
+public class ComplexClassUnitTest {
+
+    @Test
+    public void testEqualsAndHashcodes() {
+        List<String> strArrayList = new ArrayList<String>();
+        strArrayList.add("abc");
+        strArrayList.add("def");
+        ComplexClass aObject = new ComplexClass(strArrayList, new HashSet<Integer>(45, 67));
+        ComplexClass bObject = new ComplexClass(strArrayList, new HashSet<Integer>(45, 67));
+
+        List<String> strArrayListD = new ArrayList<String>();
+        strArrayListD.add("lmn");
+        strArrayListD.add("pqr");
+        ComplexClass dObject = new ComplexClass(strArrayListD, new HashSet<Integer>(45, 67));
+
+        Assert.assertTrue(aObject.equals(bObject) && bObject.equals(aObject));
+
+        Assert.assertTrue(aObject.hashCode() == bObject.hashCode());
+
+        Assert.assertFalse(aObject.equals(dObject));
+        Assert.assertFalse(aObject.hashCode() == dObject.hashCode());
+    }
+
+}

core-java-lang/src/test/java/com/baeldung/equalshashcode/entities/PrimitiveClassUnitTest.java

@@ -0,0 +1,23 @@
+package com.baeldung.equalshashcode.entities;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class PrimitiveClassUnitTest {
+
+    @Test
+    public void testTwoEqualsObjects() {
+
+        PrimitiveClass aObject = new PrimitiveClass(false, 2);
+        PrimitiveClass bObject = new PrimitiveClass(false, 2);
+        PrimitiveClass dObject = new PrimitiveClass(true, 2);
+
+        Assert.assertTrue(aObject.equals(bObject) && bObject.equals(aObject));
+
+        Assert.assertTrue(aObject.hashCode() == bObject.hashCode());
+
+        Assert.assertFalse(aObject.equals(dObject));
+        Assert.assertFalse(aObject.hashCode() == dObject.hashCode());
+    }
+
+}

core-java-lang/src/test/java/com/baeldung/equalshashcode/entities/SquareClassUnitTest.java

@@ -0,0 +1,27 @@
+package com.baeldung.equalshashcode.entities;
+
+import java.awt.Color;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import com.baeldung.equalshashcode.entities.Square;
+
+public class SquareClassUnitTest {
+
+    @Test
+    public void testEqualsAndHashcodes() {
+        Square aObject = new Square(10, Color.BLUE);
+        Square bObject = new Square(10, Color.BLUE);
+
+        Square dObject = new Square(20, Color.BLUE);
+
+        Assert.assertTrue(aObject.equals(bObject) && bObject.equals(aObject));
+
+        Assert.assertTrue(aObject.hashCode() == bObject.hashCode());
+
+        Assert.assertFalse(aObject.equals(dObject));
+        Assert.assertFalse(aObject.hashCode() == dObject.hashCode());
+    }
+
+}

core-java-lang/src/test/java/com/baeldung/generics/GenericsUnitTest.java

@@ -0,0 +1,69 @@
+package com.baeldung.generics;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.hamcrest.CoreMatchers.hasItems;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.Assert.fail;
+
+public class GenericsUnitTest {
+
+    // testing the generic method with Integer
+    @Test
+    public void givenArrayOfIntegers_thanListOfIntegersReturnedOK() {
+        Integer[] intArray = { 1, 2, 3, 4, 5 };
+        List<Integer> list = Generics.fromArrayToList(intArray);
+
+        assertThat(list, hasItems(intArray));
+    }
+
+    // testing the generic method with Integer and String type
+    @Test
+    public void givenArrayOfIntegers_thanListOfStringReturnedOK() {
+        Integer[] intArray = { 1, 2, 3, 4, 5 };
+        List<String> stringList = Generics.fromArrayToList(intArray, Object::toString);
+        assertThat(stringList, hasItems("1", "2", "3", "4", "5"));
+    }
+
+    // testing the generic method with String
+    @Test
+    public void givenArrayOfStrings_thanListOfStringsReturnedOK() {
+        String[] stringArray = { "hello1", "hello2", "hello3", "hello4", "hello5" };
+        List<String> list = Generics.fromArrayToList(stringArray);
+
+        assertThat(list, hasItems(stringArray));
+    }
+
+    // testing the generic method with Number as upper bound with Integer
+    // if we test fromArrayToListWithUpperBound with any type that doesn't
+    // extend Number it will fail to compile
+    @Test
+    public void givenArrayOfIntegersAndNumberUpperBound_thanListOfIntegersReturnedOK() {
+        Integer[] intArray = { 1, 2, 3, 4, 5 };
+        List<Integer> list = Generics.fromArrayToListWithUpperBound(intArray);
+
+        assertThat(list, hasItems(intArray));
+    }
+
+    // testing paintAllBuildings method with a subtype of Building, the method
+    // will work with all subtypes of Building
+    @Test
+    public void givenSubTypeOfWildCardBoundedGenericType_thanPaintingOK() {
+        try {
+            List<Building> subBuildingsList = new ArrayList<>();
+            subBuildingsList.add(new Building());
+            subBuildingsList.add(new House());
+
+            // prints
+            // Painting Building
+            // Painting House
+            Generics.paintAllBuildings(subBuildingsList);
+        } catch (Exception e) {
+            fail();
+        }
+    }
+
+}

core-java-lang/src/test/java/com/baeldung/hashcode/application/ApplicationUnitTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.hashcode.application;
+
+import com.baeldung.hashcode.entities.User;
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.junit.Assert.assertTrue;
+
+public class ApplicationUnitTest {
+
+    @Test
+    public void main_NoInputState_TextPrintedToConsole() throws Exception {
+        Map<User, User> users = new HashMap<>();
+        User user1 = new User(1L, "John", "john@domain.com");
+        User user2 = new User(2L, "Jennifer", "jennifer@domain.com");
+        User user3 = new User(3L, "Mary", "mary@domain.com");
+
+        users.put(user1, user1);
+        users.put(user2, user2);
+        users.put(user3, user3);
+
+        assertTrue(users.containsKey(user1));
+    }
+}

core-java-lang/src/test/java/com/baeldung/hashcode/entities/UserUnitTest.java

@@ -0,0 +1,34 @@
+package com.baeldung.hashcode.entities;
+
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+public class UserUnitTest {
+
+    private User user;
+    private User comparisonUser;
+
+    @Before
+    public void setUpUserInstances() {
+        this.user = new User(1L, "test", "test@domain.com");
+        this.comparisonUser = this.user;
+    }
+
+    @After
+    public void tearDownUserInstances() {
+        user = null;
+        comparisonUser = null;
+    }
+
+    @Test
+    public void equals_EqualUserInstance_TrueAssertion() {
+        Assert.assertTrue(user.equals(comparisonUser));
+    }
+
+    @Test
+    public void hashCode_UserHash_TrueAssertion() {
+        Assert.assertEquals(1792276941, user.hashCode());
+    }
+}

core-java-lang/src/test/java/com/baeldung/initializationguide/UserUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung.initializationguide;
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.*;
+
+import java.lang.reflect.InvocationTargetException;
+
+public class UserUnitTest {
+
+    @Test
+    public void givenUserInstance_whenIntializedWithNew_thenInstanceIsNotNull() {
+        User user = new User("Alice", 1);
+        assertThat(user).isNotNull();
+    }
+
+    @Test
+    public void givenUserInstance_whenInitializedWithReflection_thenInstanceIsNotNull() throws InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, NoSuchMethodException, SecurityException {
+        User user = User.class.getConstructor(String.class, int.class)
+            .newInstance("Alice", 2);
+        assertThat(user).isNotNull();
+    }
+
+    @Test
+    public void givenUserInstance_whenCopiedWithClone_thenExactMatchIsCreated() throws CloneNotSupportedException {
+        User user = new User("Alice", 3);
+        User clonedUser = (User) user.clone();
+        assertThat(clonedUser).isEqualTo(user);
+    }
+
+    @Test
+    public void givenUserInstance_whenValuesAreNotInitialized_thenUserNameAndIdReturnDefault() {
+        User user = new User();
+        assertThat(user.getName()).isNull();
+        assertThat(user.getId() == 0);
+    }
+}

core-java-lang/src/test/java/com/baeldung/java/diamond/Car.java

@@ -0,0 +1,5 @@
+package com.baeldung.java.diamond;
+
+public class Car<T extends Engine> implements Vehicle<T> {
+
+}

core-java-lang/src/test/java/com/baeldung/java/diamond/DiamondOperatorUnitTest.java

@@ -0,0 +1,13 @@
+package com.baeldung.java.diamond;
+
+import static org.junit.Assert.assertNotNull;
+
+import org.junit.Test;
+
+public class DiamondOperatorUnitTest {
+    @Test
+    public void whenCreateCarUsingDiamondOperator_thenSuccess() {
+        Car<Diesel> myCar = new Car<>();
+        assertNotNull(myCar);
+    }
+}

core-java-lang/src/test/java/com/baeldung/java/diamond/Diesel.java

@@ -0,0 +1,10 @@
+package com.baeldung.java.diamond;
+
+public class Diesel implements Engine {
+
+	@Override
+	public void start() {
+		System.out.println("Started Diesel...");
+	}
+
+}

core-java-lang/src/test/java/com/baeldung/java/diamond/Engine.java

@@ -0,0 +1,6 @@
+package com.baeldung.java.diamond;
+
+public interface Engine {
+
+	void start();
+}

core-java-lang/src/test/java/com/baeldung/java/diamond/Vehicle.java

@@ -0,0 +1,5 @@
+package com.baeldung.java.diamond;
+
+public interface Vehicle<T extends Engine> {
+
+}

core-java-lang/src/test/java/com/baeldung/java/doublebrace/DoubleBraceUnitTest.java

@@ -0,0 +1,46 @@
+package com.baeldung.java.doublebrace;
+
+import org.junit.Test;
+
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.stream.Stream;
+
+import static java.util.stream.Collectors.collectingAndThen;
+import static java.util.stream.Collectors.toSet;
+import static org.junit.Assert.assertTrue;
+
+public class DoubleBraceUnitTest {
+
+    @Test
+    public void whenInitializeSetWithoutDoubleBraces_containsElements() {
+        final Set<String> countries = new HashSet<>();
+        countries.add("India");
+        countries.add("USSR");
+        countries.add("USA");
+        assertTrue(countries.contains("India"));
+    }
+
+    @Test
+    public void whenInitializeSetWithDoubleBraces_containsElements() {
+        final Set<String> countries = new HashSet<String>() {
+
+            {
+                add("India");
+                add("USSR");
+                add("USA");
+            }
+        };
+        assertTrue(countries.contains("India"));
+    }
+
+    @Test
+    public void whenInitializeUnmodifiableSetWithDoubleBrace_containsElements() {
+         Set<String> countries = Stream.of("India", "USSR", "USA")
+           .collect(collectingAndThen(toSet(), Collections::unmodifiableSet));
+
+        assertTrue(countries.contains("India"));
+    }
+
+}

core-java-lang/src/test/java/com/baeldung/java/enumiteration/DaysOfWeekEnum.java

@@ -0,0 +1,31 @@
+package com.baeldung.java.enumiteration;
+
+import java.util.stream.Stream;
+
+public enum DaysOfWeekEnum {
+	SUNDAY("off"), 
+	MONDAY("working"), 
+	TUESDAY("working"), 
+	WEDNESDAY("working"), 
+	THURSDAY("working"), 
+	FRIDAY("working"), 
+	SATURDAY("off");
+
+	private String typeOfDay;
+
+	DaysOfWeekEnum(String typeOfDay) {
+		this.typeOfDay = typeOfDay;
+	}
+	
+	public String getTypeOfDay() {
+		return typeOfDay;
+	}
+
+	public void setTypeOfDay(String typeOfDay) {
+		this.typeOfDay = typeOfDay;
+	}
+
+	public static Stream<DaysOfWeekEnum> stream() {
+		return Stream.of(DaysOfWeekEnum.values());
+	}
+}

core-java-lang/src/test/java/com/baeldung/java/enumiteration/EnumIterationExamples.java

@@ -0,0 +1,18 @@
+package com.baeldung.java.enumiteration;
+
+import java.util.EnumSet;
+
+public class EnumIterationExamples {
+	public static void main(String[] args) {
+		System.out.println("Enum iteration using forEach:");
+		EnumSet.allOf(DaysOfWeekEnum.class).forEach(day -> System.out.println(day));
+
+		System.out.println("Enum iteration using Stream:");
+		DaysOfWeekEnum.stream().filter(d -> d.getTypeOfDay().equals("off")).forEach(System.out::println);
+
+		System.out.println("Enum iteration using for loop:");
+		for (DaysOfWeekEnum day : DaysOfWeekEnum.values()) {
+			System.out.println(day);
+		}
+	}
+}

core-java-lang/src/test/java/com/baeldung/java/reflection/OperationsUnitTest.java

@@ -0,0 +1,57 @@
+package com.baeldung.java.reflection;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertThat;
+
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+
+import org.junit.Test;
+
+public class OperationsUnitTest {
+
+    public OperationsUnitTest() {
+    }
+
+    @Test(expected = IllegalAccessException.class)
+    public void givenObject_whenInvokePrivateMethod_thenFail() throws NoSuchMethodException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
+        Method andPrivateMethod = Operations.class.getDeclaredMethod("privateAnd", boolean.class, boolean.class);
+
+        Operations operationsInstance = new Operations();
+        Boolean result = (Boolean) andPrivateMethod.invoke(operationsInstance, true, false);
+
+        assertFalse(result);
+    }
+
+    @Test
+    public void givenObject_whenInvokePrivateMethod_thenCorrect() throws Exception {
+        Method andPrivatedMethod = Operations.class.getDeclaredMethod("privateAnd", boolean.class, boolean.class);
+        andPrivatedMethod.setAccessible(true);
+
+        Operations operationsInstance = new Operations();
+        Boolean result = (Boolean) andPrivatedMethod.invoke(operationsInstance, true, false);
+
+        assertFalse(result);
+    }
+
+    @Test
+    public void givenObject_whenInvokePublicMethod_thenCorrect() throws Exception {
+        Method sumInstanceMethod = Operations.class.getMethod("publicSum", int.class, double.class);
+
+        Operations operationsInstance = new Operations();
+        Double result = (Double) sumInstanceMethod.invoke(operationsInstance, 1, 3);
+
+        assertThat(result, equalTo(4.0));
+    }
+
+    @Test
+    public void givenObject_whenInvokeStaticMethod_thenCorrect() throws Exception {
+        Method multiplyStaticMethod = Operations.class.getDeclaredMethod("publicStaticMultiply", float.class, long.class);
+
+        Double result = (Double) multiplyStaticMethod.invoke(null, 3.5f, 2);
+
+        assertThat(result, equalTo(7.0));
+    }
+
+}

core-java-lang/src/test/java/com/baeldung/java/reflection/ReflectionUnitTest.java

@@ -0,0 +1,302 @@
+package com.baeldung.java.reflection;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import org.junit.Test;
+
+public class ReflectionUnitTest {
+
+    @Test
+    public void givenObject_whenGetsFieldNamesAtRuntime_thenCorrect() {
+        final Object person = new Person();
+        final Field[] fields = person.getClass().getDeclaredFields();
+
+        final List<String> actualFieldNames = getFieldNames(fields);
+
+        assertTrue(Arrays.asList("name", "age").containsAll(actualFieldNames));
+    }
+
+    @Test
+    public void givenObject_whenGetsClassName_thenCorrect() {
+        final Object goat = new Goat("goat");
+        final Class<?> clazz = goat.getClass();
+
+        assertEquals("Goat", clazz.getSimpleName());
+        assertEquals("com.baeldung.java.reflection.Goat", clazz.getName());
+        assertEquals("com.baeldung.java.reflection.Goat", clazz.getCanonicalName());
+    }
+
+    @Test
+    public void givenClassName_whenCreatesObject_thenCorrect() throws ClassNotFoundException {
+        final Class<?> clazz = Class.forName("com.baeldung.java.reflection.Goat");
+
+        assertEquals("Goat", clazz.getSimpleName());
+        assertEquals("com.baeldung.java.reflection.Goat", clazz.getName());
+        assertEquals("com.baeldung.java.reflection.Goat", clazz.getCanonicalName());
+    }
+
+    @Test
+    public void givenClass_whenRecognisesModifiers_thenCorrect() throws ClassNotFoundException {
+        final Class<?> goatClass = Class.forName("com.baeldung.java.reflection.Goat");
+        final Class<?> animalClass = Class.forName("com.baeldung.java.reflection.Animal");
+        final int goatMods = goatClass.getModifiers();
+        final int animalMods = animalClass.getModifiers();
+
+        assertTrue(Modifier.isPublic(goatMods));
+        assertTrue(Modifier.isAbstract(animalMods));
+        assertTrue(Modifier.isPublic(animalMods));
+    }
+
+    @Test
+    public void givenClass_whenGetsPackageInfo_thenCorrect() {
+        final Goat goat = new Goat("goat");
+        final Class<?> goatClass = goat.getClass();
+        final Package pkg = goatClass.getPackage();
+
+        assertEquals("com.baeldung.java.reflection", pkg.getName());
+    }
+
+    @Test
+    public void givenClass_whenGetsSuperClass_thenCorrect() {
+        final Goat goat = new Goat("goat");
+        final String str = "any string";
+
+        final Class<?> goatClass = goat.getClass();
+        final Class<?> goatSuperClass = goatClass.getSuperclass();
+
+        assertEquals("Animal", goatSuperClass.getSimpleName());
+        assertEquals("Object", str.getClass().getSuperclass().getSimpleName());
+
+    }
+
+    @Test
+    public void givenClass_whenGetsImplementedInterfaces_thenCorrect() throws ClassNotFoundException {
+        final Class<?> goatClass = Class.forName("com.baeldung.java.reflection.Goat");
+        final Class<?> animalClass = Class.forName("com.baeldung.java.reflection.Animal");
+        final Class<?>[] goatInterfaces = goatClass.getInterfaces();
+        final Class<?>[] animalInterfaces = animalClass.getInterfaces();
+
+        assertEquals(1, goatInterfaces.length);
+        assertEquals(1, animalInterfaces.length);
+        assertEquals("Locomotion", goatInterfaces[0].getSimpleName());
+        assertEquals("Eating", animalInterfaces[0].getSimpleName());
+    }
+
+    @Test
+    public void givenClass_whenGetsConstructor_thenCorrect() throws ClassNotFoundException {
+        final Class<?> goatClass = Class.forName("com.baeldung.java.reflection.Goat");
+        final Constructor<?>[] constructors = goatClass.getConstructors();
+
+        assertEquals(1, constructors.length);
+        assertEquals("com.baeldung.java.reflection.Goat", constructors[0].getName());
+    }
+
+    @Test
+    public void givenClass_whenGetsFields_thenCorrect() throws ClassNotFoundException {
+        final Class<?> animalClass = Class.forName("com.baeldung.java.reflection.Animal");
+        final Field[] fields = animalClass.getDeclaredFields();
+
+        final List<String> actualFields = getFieldNames(fields);
+
+        assertEquals(2, actualFields.size());
+        assertTrue(actualFields.containsAll(Arrays.asList("name", "CATEGORY")));
+    }
+
+    @Test
+    public void givenClass_whenGetsMethods_thenCorrect() throws ClassNotFoundException {
+        final Class<?> animalClass = Class.forName("com.baeldung.java.reflection.Animal");
+        final Method[] methods = animalClass.getDeclaredMethods();
+        final List<String> actualMethods = getMethodNames(methods);
+
+        assertEquals(3, actualMethods.size());
+        assertTrue(actualMethods.containsAll(Arrays.asList("getName", "setName", "getSound")));
+    }
+
+    @Test
+    public void givenClass_whenGetsAllConstructors_thenCorrect() throws ClassNotFoundException {
+        final Class<?> birdClass = Class.forName("com.baeldung.java.reflection.Bird");
+        final Constructor<?>[] constructors = birdClass.getConstructors();
+
+        assertEquals(3, constructors.length);
+    }
+
+    @Test
+    public void givenClass_whenGetsEachConstructorByParamTypes_thenCorrect() throws Exception {
+        final Class<?> birdClass = Class.forName("com.baeldung.java.reflection.Bird");
+        birdClass.getConstructor();
+        birdClass.getConstructor(String.class);
+        birdClass.getConstructor(String.class, boolean.class);
+    }
+
+    @Test
+    public void givenClass_whenInstantiatesObjectsAtRuntime_thenCorrect() throws Exception {
+        final Class<?> birdClass = Class.forName("com.baeldung.java.reflection.Bird");
+
+        final Constructor<?> cons1 = birdClass.getConstructor();
+        final Constructor<?> cons2 = birdClass.getConstructor(String.class);
+        final Constructor<?> cons3 = birdClass.getConstructor(String.class, boolean.class);
+
+        final Bird bird1 = (Bird) cons1.newInstance();
+        final Bird bird2 = (Bird) cons2.newInstance("Weaver bird");
+        final Bird bird3 = (Bird) cons3.newInstance("dove", true);
+
+        assertEquals("bird", bird1.getName());
+        assertEquals("Weaver bird", bird2.getName());
+        assertEquals("dove", bird3.getName());
+        assertFalse(bird1.walks());
+        assertTrue(bird3.walks());
+    }
+
+    @Test
+    public void givenClass_whenGetsPublicFields_thenCorrect() throws ClassNotFoundException {
+        final Class<?> birdClass = Class.forName("com.baeldung.java.reflection.Bird");
+        final Field[] fields = birdClass.getFields();
+        assertEquals(1, fields.length);
+        assertEquals("CATEGORY", fields[0].getName());
+
+    }
+
+    @Test
+    public void givenClass_whenGetsPublicFieldByName_thenCorrect() throws Exception {
+        final Class<?> birdClass = Class.forName("com.baeldung.java.reflection.Bird");
+        final Field field = birdClass.getField("CATEGORY");
+        assertEquals("CATEGORY", field.getName());
+
+    }
+
+    @Test
+    public void givenClass_whenGetsDeclaredFields_thenCorrect() throws ClassNotFoundException {
+        final Class<?> birdClass = Class.forName("com.baeldung.java.reflection.Bird");
+        final Field[] fields = birdClass.getDeclaredFields();
+        assertEquals(1, fields.length);
+        assertEquals("walks", fields[0].getName());
+    }
+
+    @Test
+    public void givenClass_whenGetsFieldsByName_thenCorrect() throws Exception {
+        final Class<?> birdClass = Class.forName("com.baeldung.java.reflection.Bird");
+        final Field field = birdClass.getDeclaredField("walks");
+        assertEquals("walks", field.getName());
+
+    }
+
+    @Test
+    public void givenClassField_whenGetsType_thenCorrect() throws Exception {
+        final Field field = Class.forName("com.baeldung.java.reflection.Bird").getDeclaredField("walks");
+        final Class<?> fieldClass = field.getType();
+        assertEquals("boolean", fieldClass.getSimpleName());
+    }
+
+    @Test
+    public void givenClassField_whenSetsAndGetsValue_thenCorrect() throws Exception {
+        final Class<?> birdClass = Class.forName("com.baeldung.java.reflection.Bird");
+        final Bird bird = (Bird) birdClass.newInstance();
+        final Field field = birdClass.getDeclaredField("walks");
+        field.setAccessible(true);
+
+        assertFalse(field.getBoolean(bird));
+        assertFalse(bird.walks());
+
+        field.set(bird, true);
+
+        assertTrue(field.getBoolean(bird));
+        assertTrue(bird.walks());
+
+    }
+
+    @Test
+    public void givenClassField_whenGetsAndSetsWithNull_thenCorrect() throws Exception {
+        final Class<?> birdClass = Class.forName("com.baeldung.java.reflection.Bird");
+        final Field field = birdClass.getField("CATEGORY");
+        field.setAccessible(true);
+
+        assertEquals("domestic", field.get(null));
+    }
+
+    @Test
+    public void givenClass_whenGetsAllPublicMethods_thenCorrect() throws ClassNotFoundException {
+        final Class<?> birdClass = Class.forName("com.baeldung.java.reflection.Bird");
+        final Method[] methods = birdClass.getMethods();
+        final List<String> methodNames = getMethodNames(methods);
+
+        assertTrue(methodNames.containsAll(Arrays.asList("equals", "notifyAll", "hashCode", "walks", "eats", "toString")));
+
+    }
+
+    @Test
+    public void givenClass_whenGetsOnlyDeclaredMethods_thenCorrect() throws ClassNotFoundException {
+        final Class<?> birdClass = Class.forName("com.baeldung.java.reflection.Bird");
+        final List<String> actualMethodNames = getMethodNames(birdClass.getDeclaredMethods());
+
+        final List<String> expectedMethodNames = Arrays.asList("setWalks", "walks", "getSound", "eats");
+
+        assertEquals(expectedMethodNames.size(), actualMethodNames.size());
+        assertTrue(expectedMethodNames.containsAll(actualMethodNames));
+        assertTrue(actualMethodNames.containsAll(expectedMethodNames));
+
+    }
+
+    @Test
+    public void givenMethodName_whenGetsMethod_thenCorrect() throws Exception {
+        final Class<?> birdClass = Class.forName("com.baeldung.java.reflection.Bird");
+        final Method walksMethod = birdClass.getDeclaredMethod("walks");
+        final Method setWalksMethod = birdClass.getDeclaredMethod("setWalks", boolean.class);
+
+        assertFalse(walksMethod.isAccessible());
+        assertFalse(setWalksMethod.isAccessible());
+
+        walksMethod.setAccessible(true);
+        setWalksMethod.setAccessible(true);
+
+        assertTrue(walksMethod.isAccessible());
+        assertTrue(setWalksMethod.isAccessible());
+
+    }
+
+    @Test
+    public void givenMethod_whenInvokes_thenCorrect() throws Exception {
+        final Class<?> birdClass = Class.forName("com.baeldung.java.reflection.Bird");
+        final Bird bird = (Bird) birdClass.newInstance();
+        final Method setWalksMethod = birdClass.getDeclaredMethod("setWalks", boolean.class);
+        final Method walksMethod = birdClass.getDeclaredMethod("walks");
+        final boolean walks = (boolean) walksMethod.invoke(bird);
+
+        assertFalse(walks);
+        assertFalse(bird.walks());
+
+        setWalksMethod.invoke(bird, true);
+        final boolean walks2 = (boolean) walksMethod.invoke(bird);
+
+        assertTrue(walks2);
+        assertTrue(bird.walks());
+
+    }
+
+    private static List<String> getFieldNames(Field[] fields) {
+        final List<String> fieldNames = new ArrayList<>();
+        for (final Field field : fields) {
+            fieldNames.add(field.getName());
+        }
+        return fieldNames;
+
+    }
+
+    private static List<String> getMethodNames(Method[] methods) {
+        final List<String> methodNames = new ArrayList<>();
+        for (final Method method : methods) {
+            methodNames.add(method.getName());
+        }
+        return methodNames;
+    }
+
+}

core-java-lang/src/test/java/com/baeldung/loops/WhenUsingLoops.java

@@ -0,0 +1,107 @@
+package com.baeldung.loops;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+
+import org.junit.Assert;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class WhenUsingLoops {
+
+    private LoopsInJava loops = new LoopsInJava();
+    private static List<String> list = new ArrayList<>();
+    private static Set<String> set = new HashSet<>();
+    private static Map<String, Integer> map = new HashMap<>();
+
+    @BeforeClass
+    public static void setUp() {
+        list.add("One");
+        list.add("Two");
+        list.add("Three");
+
+        set.add("Four");
+        set.add("Five");
+        set.add("Six");
+
+        map.put("One", 1);
+        map.put("Two", 2);
+        map.put("Three", 3);
+    }
+
+    @Test
+    public void shouldRunForLoop() {
+        int[] expected = { 0, 1, 2, 3, 4 };
+        int[] actual = loops.simple_for_loop();
+        Assert.assertArrayEquals(expected, actual);
+    }
+
+    @Test
+    public void shouldRunEnhancedForeachLoop() {
+        int[] expected = { 0, 1, 2, 3, 4 };
+        int[] actual = loops.enhanced_for_each_loop();
+        Assert.assertArrayEquals(expected, actual);
+    }
+
+    @Test
+    public void shouldRunWhileLoop() {
+        int[] expected = { 0, 1, 2, 3, 4 };
+        int[] actual = loops.while_loop();
+        Assert.assertArrayEquals(expected, actual);
+    }
+
+    @Test
+    public void shouldRunDoWhileLoop() {
+        int[] expected = { 0, 1, 2, 3, 4 };
+        int[] actual = loops.do_while_loop();
+        Assert.assertArrayEquals(expected, actual);
+    }
+
+    @Test
+    public void whenUsingSimpleFor_shouldIterateList() {
+        for (int i = 0; i < list.size(); i++) {
+            System.out.println(list.get(i));
+        }
+    }
+
+    @Test
+    public void whenUsingEnhancedFor_shouldIterateList() {
+        for (String item : list) {
+            System.out.println(item);
+        }
+    }
+
+    @Test
+    public void whenUsingEnhancedFor_shouldIterateSet() {
+        for (String item : set) {
+            System.out.println(item);
+        }
+    }
+
+    @Test
+    public void whenUsingEnhancedFor_shouldIterateMap() {
+        for (Entry<String, Integer> entry : map.entrySet()) {
+            System.out.println("Key: " + entry.getKey() + " - " + "Value: " + entry.getValue());
+        }
+    }
+
+    @Test
+    public void whenUsingSimpleFor_shouldRunLabelledLoop() {
+        aa: for (int i = 1; i <= 3; i++) {
+            if (i == 1)
+                continue;
+            bb: for (int j = 1; j <= 3; j++) {
+                if (i == 2 && j == 2) {
+                    break aa;
+                }
+                System.out.println(i + " " + j);
+            }
+        }
+    }
+
+}

core-java-lang/src/test/java/com/baeldung/nestedclass/AnonymousInner.java

@@ -0,0 +1,20 @@
+package com.baeldung.nestedclass;
+
+import org.junit.Test;
+
+abstract class SimpleAbstractClass {
+    abstract void run();
+}
+
+public class AnonymousInner {
+
+    @Test
+    public void run() {
+        SimpleAbstractClass simpleAbstractClass = new SimpleAbstractClass() {
+            void run() {
+                System.out.println("Running Anonymous Class...");
+            }
+        };
+        simpleAbstractClass.run();
+    }
+}

core-java-lang/src/test/java/com/baeldung/nestedclass/Enclosing.java

@@ -0,0 +1,21 @@
+package com.baeldung.nestedclass;
+
+import org.junit.Test;
+
+public class Enclosing {
+
+    private static int x = 1;
+
+    public static class StaticNested {
+
+        private void run() {
+            System.out.println("x = " + x);
+        }
+    }
+
+    @Test
+    public void test() {
+        Enclosing.StaticNested nested = new Enclosing.StaticNested();
+        nested.run();
+    }
+}

core-java-lang/src/test/java/com/baeldung/nestedclass/NewEnclosing.java

@@ -0,0 +1,22 @@
+package com.baeldung.nestedclass;
+
+import org.junit.Test;
+
+public class NewEnclosing {
+
+    private void run() {
+        class Local {
+            void run() {
+                System.out.println("Welcome to Baeldung!");
+            }
+        }
+        Local local = new Local();
+        local.run();
+    }
+
+    @Test
+    public void test() {
+        NewEnclosing newEnclosing = new NewEnclosing();
+        newEnclosing.run();
+    }
+}

core-java-lang/src/test/java/com/baeldung/nestedclass/NewOuter.java

@@ -0,0 +1,30 @@
+package com.baeldung.nestedclass;
+
+import org.junit.Test;
+
+public class NewOuter {
+
+    int a = 1;
+    static int b = 2;
+
+    public class InnerClass {
+        int a = 3;
+        static final int b = 4;
+
+        public void run() {
+            System.out.println("a = " + a);
+            System.out.println("b = " + b);
+            System.out.println("NewOuter.this.a = " + NewOuter.this.a);
+            System.out.println("NewOuter.b = " + NewOuter.b);
+            System.out.println("NewOuter.this.b = " + NewOuter.this.b);
+        }
+    }
+
+    @Test
+    public void test() {
+        NewOuter outer = new NewOuter();
+        NewOuter.InnerClass inner = outer.new InnerClass();
+        inner.run();
+
+    }
+}

core-java-lang/src/test/java/com/baeldung/nestedclass/Outer.java

@@ -0,0 +1,20 @@
+package com.baeldung.nestedclass;
+
+import org.junit.Test;
+
+public class Outer {
+
+    public class Inner {
+
+        public void run() {
+            System.out.println("Calling test...");
+        }
+    }
+
+    @Test
+    public void test() {
+        Outer outer = new Outer();
+        Outer.Inner inner = outer.new Inner();
+        inner.run();
+    }
+}

core-java-lang/src/test/java/com/baeldung/primitiveconversion/PrimitiveConversionsJUnitTest.java

@@ -0,0 +1,126 @@
+package com.baeldung.primitiveconversion;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import static org.junit.Assert.assertEquals;
+
+public class PrimitiveConversionsJUnitTest {
+
+    private static final Logger LOG = LoggerFactory.getLogger(PrimitiveConversionsJUnitTest.class);
+    
+    @Test
+    public void givenDataWithLessBits_whenAttributingToLargerSizeVariable_thenNoSpecialNotation() {
+        int myInt = 127;
+        
+        long myLong = myInt;
+        assertEquals(127L, myLong);
+        
+        float myFloat = myLong;
+        assertEquals(127.0f, myFloat, 0.00001f);
+        
+        double myDouble = myLong;
+        assertEquals(127.0, myDouble,0.00001);
+    }
+    
+    @Test
+    public void givenDataWithMoreBits_whenAttributingToSmallerSizeVariable_thenCastOperatorNeeded() {
+        
+        long myLong = 127L;
+        double myDouble = 127.0;
+        
+        float myFloat = (float) myDouble;
+        assertEquals(127.0f, myFloat, 0.00001f);
+        
+        int myInt = (int) myLong;
+        assertEquals(127, myInt);
+        
+        byte myByte = (byte) myInt;
+        assertEquals( ((byte)127), myByte);
+    }
+    
+    @Test
+    public void givenPrimitiveData_whenAssiginingToWrapper_thenAutomaticBoxingHappens(){
+        int myInt = 127;
+        
+        Integer myIntegerReference = myInt;
+        assertEquals(new Integer("127"), myIntegerReference);
+        
+    }
+    
+    @Test
+    public void givenWrapperObjectData_whenAssiginingToPrimitive_thenAutomaticUnboxingHappens(){
+        Integer myIntegerReference = new Integer("127");
+        
+        int myOtherInt = myIntegerReference;
+        assertEquals(127, myOtherInt);
+        
+    }
+    
+    @Test
+    public void givenByteValue_whenConvertingToChar_thenWidenAndNarrowTakesPlace(){
+        byte myLargeValueByte = (byte) 130;   //0b10000010
+        LOG.debug("{}", myLargeValueByte); //0b10000010 -126
+        assertEquals( -126, myLargeValueByte);
+        
+        int myLargeValueInt = myLargeValueByte;
+        LOG.debug("{}", myLargeValueInt); //0b11111111 11111111 11111111 10000010 -126
+        assertEquals( -126, myLargeValueInt);
+        
+        char myLargeValueChar = (char) myLargeValueByte;
+        LOG.debug("{}", myLargeValueChar);//0b11111111 10000010 unsigned 0xFF82
+        assertEquals(0xFF82, myLargeValueChar);
+        
+        myLargeValueInt = myLargeValueChar;
+        LOG.debug("{}", myLargeValueInt); //0b11111111 10000010  65410
+        assertEquals(65410, myLargeValueInt);
+        
+        byte myOtherByte = (byte) myLargeValueInt;
+        LOG.debug("{}", myOtherByte); //0b10000010 -126
+        assertEquals( -126, myOtherByte);
+        
+        
+        char myLargeValueChar2 = 130; //This is an int not a byte!
+        LOG.debug("{}", myLargeValueChar2);//0b00000000 10000010 unsigned 0x0082
+        assertEquals(0x0082, myLargeValueChar2);
+        
+        int myLargeValueInt2 = myLargeValueChar2;
+        LOG.debug("{}", myLargeValueInt2); //0b00000000 10000010  130
+        assertEquals(130, myLargeValueInt2);
+        
+        byte myOtherByte2 = (byte) myLargeValueInt2;
+        LOG.debug("{}", myOtherByte2); //0b10000010 -126
+        assertEquals( -126, myOtherByte2);
+    }
+    
+    @Test
+    public void givenString_whenParsingWithWrappers_thenValuesAreReturned(){
+        String myString = "127";
+        
+        byte  myNewByte   = Byte.parseByte(myString);
+        assertEquals( ((byte)127), myNewByte);
+        
+        short myNewShort  = Short.parseShort(myString);
+        assertEquals( ((short)127), myNewShort);
+        
+        int   myNewInt    = Integer.parseInt(myString);
+        assertEquals( 127, myNewInt);
+        
+        long  myNewLong   = Long.parseLong(myString);
+        assertEquals( 127L, myNewLong);
+        
+        float  myNewFloat  = Float.parseFloat(myString);
+        assertEquals( 127.0f, myNewFloat, 0.00001f);
+        
+        double myNewDouble = Double.parseDouble(myString);
+        assertEquals( 127.0, myNewDouble, 0.00001f);
+        
+        boolean myNewBoolean = Boolean.parseBoolean(myString);
+        assertEquals( false, myNewBoolean); //numbers are not true!
+        
+        char myNewChar = myString.charAt(0);
+        assertEquals( 49, myNewChar); //the value of '1'
+    }
+    
+}

core-java-lang/src/test/java/com/baeldung/staticdemo/CarIntegrationTest.java

@@ -0,0 +1,14 @@
+package com.baeldung.staticdemo;
+
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+
+public class CarIntegrationTest {
+    @Test
+    public void whenNumberOfCarObjectsInitialized_thenStaticCounterIncreases() {
+        new Car("Jaguar", "V8");
+        new Car("Bugatti", "W16");
+        assertEquals(2, Car.numberOfCars);
+    }
+}

core-java-lang/src/test/java/com/baeldung/staticdemo/SingletonIntegrationTest.java

@@ -0,0 +1,15 @@
+package com.baeldung.staticdemo;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class SingletonIntegrationTest {
+
+    @Test
+    public void givenStaticInnerClass_whenMultipleTimesInstanceCalled_thenOnlyOneTimeInitialized() {
+        Singleton object1 = Singleton.getInstance();
+        Singleton object2 = Singleton.getInstance();
+        
+        Assert.assertSame(object1, object2);
+    }
+}

core-java-lang/src/test/java/com/baeldung/staticdemo/StaticBlockIntegrationTest.java

@@ -0,0 +1,17 @@
+package com.baeldung.staticdemo;
+
+import static org.hamcrest.collection.IsIterableContainingInOrder.contains;
+import static org.junit.Assert.assertThat;
+
+import java.util.List;
+
+import org.junit.Test;
+
+public class StaticBlockIntegrationTest {
+
+    @Test
+    public void whenAddedListElementsThroughStaticBlock_thenEnsureCorrectOrder() {
+        List<String> actualList = StaticBlock.getRanks();
+        assertThat(actualList, contains("Lieutenant", "Captain", "Major", "Colonel", "General"));
+    }
+}

core-java-lang/src/test/java/com/baeldung/varargs/FormatterUnitTest.java

@@ -0,0 +1,60 @@
+package com.baeldung.varargs;
+
+import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+public class FormatterUnitTest {
+
+    private final static String FORMAT = "%s %s %s";
+
+    @Test
+    public void givenNoArgument_thenEmptyAndTwoSpacesAreReturned() {
+        String actualResult = format();
+
+        assertThat(actualResult, is("empty  "));
+    }
+
+    @Test
+    public void givenOneArgument_thenResultHasTwoTrailingSpace() {
+        String actualResult = format("baeldung");
+
+        assertThat(actualResult, is("baeldung  "));
+    }
+
+    @Test
+    public void givenTwoArguments_thenOneTrailingSpaceExists() {
+        String actualResult = format("baeldung", "rocks");
+
+        assertThat(actualResult, is("baeldung rocks "));
+    }
+
+    @Test
+    public void givenMoreThanThreeArguments_thenTheFirstThreeAreUsed() {
+        String actualResult = formatWithVarArgs("baeldung", "rocks", "java", "and", "spring");
+
+        assertThat(actualResult, is("baeldung rocks java"));
+    }
+
+    public String format() {
+        return format("empty", "");
+    }
+
+    public String format(String value) {
+        return format(value, "");
+    }
+
+    public String format(String val1, String val2) {
+        return String.format(FORMAT, val1, val2, "");
+    }
+
+    public String formatWithVarArgs(String... values) {
+        if (values.length == 0) {
+            return "no arguments given";
+        }
+
+        return String.format(FORMAT, values);
+    }
+
+}